Electronic load module and a method and a system therefor

ABSTRACT

The present invention relates to an electronic load module and to a method and a system therefor. The method comprises receiving control data ( 301 ) from a connectable power controller via a data bus connector ( 202 ), and controlling ( 302 ) an active load ( 203 ) based on the received control data to sink a defined current from a connectable device under test via a first input ( 204 ). The method further comprises controlling ( 303 ) the activate load ( 203 ) based on the received control data by means of a digital control circuit ( 201 ) and the connectable power controller to generate and maintain an ambient temperature of the device under test.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a 35 U.S.C. §371 National Phase Entry Applicationfrom PCT/EP2012/076781, filed Dec. 21, 2012, designating the UnitedStates, the disclosure of which is incorporated herein in its entiretyby reference.

TECHNICAL FIELD

The present disclosure relates to an electronic load, and moreparticularly to an electronic load module configured for testing powersupply systems on a printed board assembly as well as a method and asystem therefor.

BACKGROUND

Modern integrated circuits, IC, consume more and more power at lowersupply voltages. Therefore, the traditional approach of deliveringconverted power from a power supply unit (PSU) at the right voltage tothe IC on a printed circuit board (PCB) via a connector on the PCB is nolonger a viable solution. This can easily be understood by simplecalculations using ohms law: an IC with a supply voltage of 2.2 V and apower consumption of 30 W requires a current of approximately 13 A. APSU with such ratings exhibits large ohmic losses due to the resistanceof the leads from the PSU to the IC.

A common solution to this problem is to place the PSU close to the IC onthe PCB and to utilize an intermediate bus voltage provided to the PSUon the PCB via a connector. It is also common today to integrate a powercontroller on the PCB that controls all PSU's with a dedicated bus, suchas a PMBUS for example.

This results in PCB's comprising several intertwined subsystems relatedto different functions of the circuit. One critical subsystem is thepower supply system. The power supply system must provide large powerconsumers, such as a field programmable gate array (FPGA) circuit, withstable power at low supply voltage and high current. Especially thephase of turning on a FPGA circuit proves to be very demanding for thePSU since it is usually recommended to ramp-up the supply voltage in acontrolled manner.

During the development of a modern PCB it is frequently desired to testeach subsystem separately before integrating the full system on the PCB.Hence, in order to test the PSU system on the PCB an electronic load isneeded to replace the current consuming subcircuits such as the FPGAcircuit.

Such an electronic load is commonly available as bench-top equipment andrack mounted devices connected to the PCB by means of leads andconnectors.

Another aspect to test is the effect of the environment on the PCB, andespecially temperature effects on the stability and functionality of thepower supply system on the PCB.

This environmental test is usually performed in an environmental testchamber, see FIG. 1. Such an environmental test is performed by placingthe PCB in the chamber with the electric load connected to the powersupply system. The temperature in the chamber is gradually increaseduntil the desired working temperature is reached. Then the electricaltest of the power supply system is performed by turning on the powersupply system and variate the electrical load to simulate differentworking conditions.

Some problems exists with this setup. First, the environmental testchamber is usually quite expensive and bulky. Secondly, the leadsconnecting the electronic load to the PCB are usually long and causeparasitic inductances and capacitances between the electronic load andthe PCB. Such parasitic effects makes it difficult to correctly simulateslew-rate effects on the PCB by means of the electronic load.

SUMMARY

An object is therefore to address the problems and disadvantagesoutlined above, and to provide an improved electronic load module aswell as a system and a method.

This object and others are achieved by the method, the electronic loadmodule and the system according to the independent claims, and by theembodiments according to the dependent claims.

In accordance with one embodiment a method for operating an electronicload module is provided. The electronic load module comprises a digitalcontrol circuit configured to be connected to a power controller via adata bus connector, an active load operatively connected to andcontrolled by said digital control circuit and a first input operativelyconnected to the active load and configured to be connected to a deviceunder test. The method comprises receiving control data from saidconnectable power controller via the data bus connector, and controllingthe active load based on the received control data to sink a definedcurrent from said connectable device under test via the first input. Themethod also comprises controlling the activate load based on thereceived control data by means of the digital control circuit and theconnectable power controller to generate and maintain an ambienttemperature of the device under test.

In accordance with another embodiment, an electronic load module isprovided. The electronic load module comprises a digital control circuitconfigured to be connected to a power controller via a data busconnector, an active load operatively connected to and controlled bysaid digital control circuit, and a first input operatively connected tothe active load and configured to be connected to a device under test.The digital control circuit is configured to receive control data fromsaid connectable power controller via the data bus connector. Thedigital control circuit is further configured to control the active loadto sink a defined current from said device under test via the firstinput. The activate load of the electronic load module is configured tobe controlled by said digital control circuit to generate and maintainan ambient temperature of the connectable device under test.

In accordance with yet another embodiment a system for electricalloading of a device under test is provided. The system comprises a powercontroller configured to control at least one power converter circuitwithin the device under test, a physical housing of the device undertest, and a temperature sensor operatively connected to said powercontroller and being configured to measure an ambient temperature insidesaid physical housing. The system further comprises an electronic loadmodule configured to be controlled by said power controller and beingconfigured to be arranged within the device under test. The electronicload module comprises an active load configured to sink a current fromsaid device under test. The electronic load module of the system isconfigured to generate and maintain a defined ambient temperature withinthe physical housing of the device under test using the active load, and

the power controller is configured to control the ambient temperaturewithin the physical housing based on said measured temperature and bymeans of the electronic load module.

An advantage of particular embodiments is that the conventionalenvironmental test chamber becomes unnecessary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of a conventional setup of a load testsystem.

FIG. 2 is a schematic block diagram of an inventive electronic loadmodule.

FIG. 3 is a flowchart of the method performed by the electronic loadmodule of FIG. 2.

FIG. 4 is a schematic block diagram of an electronic load module with asecond input and a computer interface.

FIG. 5 is a schematic block circuit diagram of an active load of theelectronic load module.

FIG. 6 is a schematic block diagram of an electronic load systemincorporating the electronic load module of FIG. 5.

FIG. 7 is a schematic block diagram of an alternative electronic loadsystem.

DETAILED DESCRIPTION

In the following, different aspects will be described in more detailwith references to certain embodiment and to the accompanying drawings.For purposes of explanation and without intention of limitation,specific details are set forth, such as particular scenarios andtechniques, in order to provide a thorough understanding of thedifferent embodiments. However, other embodiments that depart from thesespecific details may also exist.

FIG. 1 is a schematic drawing of a conventional measurement set up,generally designated 100, for performing measurements at elevatedtemperatures. This setup comprises an environmental test chamber 101that can control the temperature inside the same. Inside theenvironmental test chamber 101 is a device under test (DUT) 103arranged. The DUT 103 can be a PCB or a complete device with an internalPSU. To test the PSU of the DUT it is suitable to connect an electronicload 102 to the PSU. In order to connect the electronic load 102 to theDUT 103 leads 104 are arranged there between. These leads 104 areusually relatively thick in order to minimize the impact of ohmiclosses.

A severe drawback of this system is the parasitic inductances andcapacitances caused by the long leads 104. These parasitic componentsmake it very hard to perform precise slew-rate measurements on the DUT103.

Another drawback is related to the measurement setup itself. Byarranging the electronic load 102 separated from the DUT 103 localheating effects in the DUT 103 is not captured during the measurement.

Therefore, it would be beneficial if these drawbacks could be obviated.

This disclosure describes a feasible way to overcome the shortcomings ofthe conventional setup system 100.

Generally, a modern electronic circuit on a PCB often comprises somecircuits that have huge power demands at low supply voltages. Such acircuit might be a Field Programmable Gate Array (FPGA). In order tofulfill the power need from the FPGA the PCB often includes severalpoint of load (POL) voltage converters. These POL regulators are usuallyconnected to a power controller via a dedicated bus, such as a powermanagement bus (PMBUS). The power controller is configured to controleach of the POL regulators via said dedicated bus.

FIG. 2 is a schematic block diagram of an embodiment of an electronicload module, generally designated 200. The electronic load module 200comprises a digital control circuit 201 configured to be connected tothe power controller mentioned above via a data bus connector 202. Thedigital control circuit 201 is further connected to an active load 203.The active load 203 further comprises a first input 204 configured to beconnected to a OUT. The active load 203 is configured to sink a definedcurrent from the first input 204 to ground potential and to generate andmaintain an ambient temperature of the connectable OUT. The control ofthe active load 203 to sink the defined current or to generate heat,respectively, is performed by the digital control circuit 201 and theconnectable power controller.

The control of the electronic load module is performed according to amethod disclosed in the flowchart in FIG. 3. The method 300 comprises:

301: Receive control data from the connectable power controller via thedata bus connector 204. This control data may comprise defined settemperatures and defined set currents.

302: Control the active load to sink a defined current from saidconnectable DUT via the first input 204.

303: Control the active load by means of the digital control circuit andthe connectable power controller to generate and maintain the ambienttemperature of the DUT. This step of the method uses the active load asa heating device for providing the necessary heat in order to bring theOUT to the defined temperature.

In one embodiment, the electronic load module 200 may be arranged toreplace a FPGA on a PCB during a test phase. The electronic load module200 may be in thermal contact with a heat sink provided for the FPGA.

In FIG. 4 another embodiment of the electronic load module 200 isdisclosed. In this embodiment is the digital control circuit providedwith a computer interface 401 that is configured to be connected to anexternal computer. This computer interface may be used to reprogram thedigital control circuit 201. In one embodiment the computer interface isa JTAG interface.

In one embodiment comprises the active load 203 a second input 400configured for supplying the active load 203 with external power from anexternal power supply for the purpose of heating.

An embodiment of an active load 203 will now be disclosed with referencemade to FIG. 5. The active load 203 comprises said selector circuit 501with the first input 204 configured to be connected to a DUT. The secondinput 400 of the active load 203 is configured to be connected to anexternal power supply for heating purposes. The selector circuit furthercomprises a select input 502 configured to receive a select signal fromthe digital control circuit 201.

The active load further comprises a control input 503 configured forreceiving an analog control signal from the digital control circuit 201.This analog control signal from the digital control circuit 201 may begenerated by a digital to analog converter of the digital controlcircuit 201.

The active load 203 further comprises a MOSFET transistor T1 with thedrain thereof connected to an output of said selector circuit 501, andthe source being connected to ground potential via a first resistor R1.

The active load 203 further comprises an operational amplifier OP1having the non-inverting input connected to the output of a bufferamplifier A1. The input of the buffer amplifier A1 is configured to beconnected to said digital control circuit 201 via said control input503, the inverting input of the operational amplifier OP1 beingconnected to the source of the MOSFET transistor via a second resistorR2 forming a feedback loop, and the output of the operational amplifierOP1 is connected to the inverting input of the operational amplifier OP1via a third resistor R3 and a first capacitor C1. The output of theoperational amplifier OP1 is further connected to the gate of the MOSFETtransistor T1.

The operation of the active load 203 will now be described withreference made to FIG. 5 using a first scenario and a second scenario.

In the first scenario the first input 204 is selected by said selectsignal from the digital control circuit 201. By applying a controlvoltage to the control input 503 the buffer amplifier A1 applies thecontrol voltage to the non-inverting input of the operational amplifierOP1. Due to the first feedback branch the operational amplifier willadjust its output voltage in order to achieve zero voltage offsetbetween the non-inverting input and the inverting input of theoperational amplifier OP1. Hence, the MOSFET transistor will beactivated by means of the voltage potential of the gate thereof causedby the output of the operational amplifier OP1 causing a current throughthe first resistor R1. The current through the first resistor R1 causesa voltage drop over the first resistor R1. This voltage drop is fed backto the inverting input of the operational amplifier OP1. In this firstscenario the current through the first resistor R1 is controlled bymeans of the control voltage at the control input 503.

In the second scenario the second input 400 is selected by said selectsignal from the digital control circuit 201. The second input 400 isconfigured to be connected to the external power supply. In this secondscenario, the purpose of connecting an external power supply is to usethe MOSFET transistor to dissipate heat by flowing a current through thesame. In this scenario the control voltage at the control input 503 isused to control the amount of heat that the MOSFET transistordissipates.

FIG. 6 is a schematic block diagram of an embodiment of a system 600 forelectrical loading of a DUT 601. The system comprises a power controller602 configured to control at least one power converter circuit 605within the DUT 601, and a physical housing 603 of the DUT 601. Thishousing 603 is used to shield the DUT 601 from the surroundingenvironment. This housing could also be a RF shield.

The system 600 further comprises a temperature sensor 604 operativelyconnected to said power controller 602 and being configured to measure atemperature inside said physical housing 603.

The system 600 further comprises an electronic load module 200configured to be controlled by said power controller 602 and beingconfigured to be arranged within the DUT 601. The electronic load module200 comprises an active load 203 configured to sink a current from saidDUT 601

The electronic load module 200 is configured to generate and maintain adefined temperature within the housing 603 of the DUT 601 using theactive load 203. The power controller 602 is configured to control thetemperature within the physical housing 603 based on said measuredtemperature by means of the electronic load module 200.

Another embodiment of a system for electrical loading of a DUT is nowdisclosed with reference to FIG. 7. In this embodiment an external powersupply 701 is connected to the second input 400 of the active load 203.This external power supply may be used to generate heat and to maintainthe temperature within said housing 603. The whole test sequence iscontrolled and supervised via a control computer 702. The controlcomputer 702 is operatively connected to the power controller 602 bymeans of for example a computer bus such as a PMBUS.

The operation of this system can shortly be described as: measure theambient temperature within the DUT 601 with the temperature sensor 604and send the temperature data to the control computer 702. If it isdetermined by the control computer 702 that the temperature must beincreased, a command is sent from the control computer 702 via the powercontroller 602 to the electronic load module 200. The digital controlcircuit 201 of the electronic load module 200 selects the second input400 as an input source. Hence, the DUT 601 is disconnected from theelectronic load module 200 by means of the selector circuit 501. Theactive load 203 is then used to generate heat within the DUT 601 and thehousing 603. This heating is supervised and controlled by the powercontroller 602 and the control computer 702. When the defined ambienttemperature within the DUT 601 is reached, the external power supply isdisconnected. At this point the DUT 601 is ready for testing by means ofthe electronic load module 200. A test program emulating differentloading conditions is then executed by the control computer 702 andperformed by the electronic load module 200. If it is determined thatthe DUT 601 needs some extra heating during the test sequence, theexternal power supply is then temporarily connected and used to heat theDUT 601.

In one embodiment is the electronic load module 200 configured to be pincompatible with a circuit in the DUT and to use existing heatsinkswithin the DUT to dissipate heat. In this way realistic temperaturedistributions within the DUT 601 can be achieved.

Such a mounting of the electronic load module within the DUT 601 alsoenables realistic slew-rate tests. That may emulate the power-onsequence for a FPGA circuit. This can be attributed to the fact thatlong leads connecting a DUT to the electronic load is eliminated, orsignificantly reduced, resulting in a minimization of the parasiticelements.

In order to further illustrate the beneficial features of the systemsome exemplary scenarios will now be disclosed.

In the first exemplary scenario a PCB comprising a FPGA circuit will bedescribed. The DUT 601 in this first exemplary scenario is a PCB withfunctions relating to a telecommunication system. The physical housing603 of this DUT 601 is provided for RF shielding. In order to havesufficient power for the FPGA circuit a modern distributed PSS isutilized. This PSS comprises a power controller 602 operativelyconnected to several POL converters by means of a PMBUS. The designersof this PCB wants to test the capabilities of the PSS under differentworking conditions, unfortunately the FPGA sub-circuit is not ready fortesting at this early stage of development. It is therefore desired toemulate the loading by the FPGA on the PSS by means of the electronicload module 200. The electronic load module is configured to be pincompatible with the FPGA circuit, and therefore the electronic loadmodule 200 is a drop-in replacement for the FPGA circuit. The MOSFET T1of the active load 203 is configured to be thermally connected to theheatsink of the FPGA. The electronic load module 200 is furtherconfigured to be controlled by Instructions received from the PMBUS viathe data bus connector 202. In this way no extra control leads areneeded to control the electronic load module. The control computer 702is connected to the power controller via a USB to PMBUS converter.

In this scenario no environmental test chamber is required and no longleads are required to connect the electronic load module 200 to the PCB.Hence, a very realistic test of the DUT is possible including thedemanding slew-rate measurements.

In a second exemplary embodiment several active loads 203 are connectedto the digital control circuit 201. Accordingly, the electronic loadmodule can generate heat and sink current simultaneously.

The above mentioned and described embodiments are given only as examplesand should not be limiting to the present invention.

ABBREVIATIONS

DUT Device Under Test

FPGA Field Programmable Gate Array

JTAG Joint Test Acton Group

PCB Printed Circuit Board

PMBUS Power Management BUS

POL Point Of Load

PSS Power Supply System

PSU Power Supply Unit

The invention claimed is:
 1. A method for operating an electronic load module, wherein the electronic load module comprises: a digital control circuit configured to be connected to a power controller via a data bus connector; an active load operatively connected to and controlled by said digital control circuit; and a first input operatively connected to the active load and configured to be connected to a device under test; wherein the method comprises: receiving control data from said connectable power controller via the data bus connector; controlling the active load based on the received control data using the digital control circuit and the connectable power controller to generate and maintain an ambient temperature of the device under test and to sink a defined current from said connectable device under test via the first input.
 2. The method according to claim 1, wherein the electronic load module comprises a second input connected to said active load and being configured to be connected to an external power supply, wherein said active load is configured to be controlled by the digital control circuit to select the first input or the second input for receiving power, wherein the method further comprises: controlling the active load based on the received control data to receive power from said second input causing the active load to produce heat by using said connectable external power supply.
 3. The method according to claim 1, wherein the electronic load module further comprises a computer interface connected to said digital control circuit and being configured to be connected to an external computer, wherein the method further comprises reprogramming the digital control circuit by said external computer via said computer interface.
 4. An electronic load module comprising: a digital control circuit configured to be connected to a power controller via a data bus connector; an active load operatively connected to and controlled by said digital control circuit; and a first input operatively connected to the active load and configured to be connected to a device under test, wherein the digital control circuit is configured to receive control data from said connectable power controller via the data bus connector and to control the active load, based on the received control data, to sink a defined current from said device under test via the first input, wherein the active load is configured to be controlled by said digital control circuit, based on the received control data, to generate and maintain an ambient temperature of the connectable device under test.
 5. The electronic load module according to claim 4, comprising a second input being connected to a selector circuit of said active load and configured to be connected to an external power supply, wherein the selector circuit is configured to selectively provide power from either the connectable device under test or the connectable external power supply to the active load.
 6. The electronic load module according to claim 5, wherein said active load comprises: said selector circuit being connected to the first input and to the second input; a MOSFET transistor with the drain thereof connected to an output of said selector circuit, and the source being connected to ground potential via a first resistor; an operational amplifier having the non-inverting input connected to the output of a buffer amplifier, the input of the buffer amplifier is configured to be connected to said digital control circuit via a control input, the inverting input of the operational amplifier is connected to the source of the MOSFET transistor via a second resistor forming a feedback loop, and the output of the operational amplifier is connected to the inverting input of the operational amplifier via a branch comprising a third resistor and a first capacitor, the output of the operational amplifier is further connected to the gate of the MOSFET transistor; whereby the current through the MOSFET transistor is controlled by said digital control circuit, and by controlling the selector circuit can the connectable external power supply be selected to supply power to said MOSFET transistor for generating heat.
 7. The electronic load module according to claim 4, comprising a computer interface connected to said digital control circuit and being configured to be connected to an external computer, wherein the digital control circuit can be reprogrammed by said external computer via said computer interface.
 8. A system for electrical loading of a device under test, wherein the system comprises: a power controller configured to control at least one power converter circuit within the device under test; a physical housing of the device under test; a temperature sensor operatively connected to said power controller and being configured to measure an ambient temperature inside said physical housing; an electronic load module configured to be controlled by said power controller and being configured to be arranged within the device under test, wherein the electronic load module comprises an active load and a digital control circuit configured to receive control data from the power controller and to control the active load, based on the received control data, to sink a defined current from said device under test, and wherein the electronic load module is configured to generate and maintain a defined ambient temperature within the physical housing of the device under test using the active load, which is controlled by the digital control circuit based on the received control data, and the power controller is configured to control the ambient temperature within the physical housing based on said measured ambient temperature and by the electronic load module.
 9. The system according to claim 8, comprising an external power supply, and wherein the electronic load module comprises a second input for receiving power from the external power supply, the electronic load module is further configured to select either the device under test or the external power supply for sinking current and generating heat, respectively.
 10. The system according to claim 8, comprising a control computer operatively connected to said power controller and being configured for communication with the power controller, wherein the communication comprises sending instructions about said defined temperature within the physical housing and loading instructions. 